Apparatus for determining leaks in drill pipe



Oct. 26, 1943. R. I. GARDNER I 2,332,557

APPARATUS FOR DETERMINING LEAKS IN DRILL PIPE Filed Feb. 26, 1941 3Sheets-Sheet 1 I L DRILL/N6 Flu/0 p/PE INVENTOR ATTORNEYS Oct. 26, 1943.R. I. GARDNER 2,332,567 I APPARATUS FOR DETERMINING LEAKS IN DRILL PIPEFiled Feb. 26, 1941 3 Sheets-Sheet 2 INVENTO P0669? Z Gardner ATTORNEY5'1 Oct. 26, 1943. R. I. GARDNER APPARATUS FOR DETERMINING LEAKSv I NDRILL PIPE Filed Feb. 26, 1941 v5 Sheets-Sheet 5 INVENTOR W m a Z rv...E i

Patented Oct. 26, 1943 H UNITED STATES PATENT- OFFICE- APPARATUS FORDETERMINING LEAKS IN mum. PIPE Robert I. Gardner, Bakersfield, CaliL,assignor to Richfiield Oil Corporation, Los Angeles, Calif., acorporation of Delaware Application February 26, 1941, Serial No.380,657

2 Claims.

This invention relates to well drilling and is concerned particularlywith the detection of leaks or washouts in drill pipe.

In the drilling of Wells with a rotary rig, a

a substantially constant relationship to the pressure at theunobstructed point as long as there are no leaks in the drill pipe, orcave-ins in the hole irrespective of other changes in the drillingcircuit. If, however, a leak or cave-in turi tube string of drill pipebearing a bit or cutting tool 5 occurs, it is indicated by a change insaid relaat its lower end is rotated in the hole, and cuttionship. tingsare removed from the bottom of the hole Observation of variations fromthe relationby means of a current of drilling fluid (mud) ship whichprevails when there are no leaks in that is delivered to the bit throughthe drill pipe the drill pipemay be made conveniently by con and isreturned to the topof the well through nectinga first pressure gauge soas to determine the bored hole outside the pipe. the differentialpressure existing between the ob- When a leak occurs in the drill pipe,immedi-' structed and unobstructed point in/th pipe andate detection ishighly desirable; otherwise the a second pressure gauge to determine thepresleak will be enlarged by erosive action of the sure at theunobstructed point, and by causing solids in the mud until the pipe isbroken, The the two gauges to cooperate to indicate a'change portion ofthe drill pipe below the break is thus in the relationship of thequantities determined detached and lost. This necessitates a time conbythe respective gauges. For example, the point suming and expensivefishing operation. at which the obstruction occurs in the drillingHeretofore, many fishing operations have resulted fluid pipe may beconnected to one end of a difbecause a satisfactory means for detectingleaks ferential pressure gauge, a point preceding it in asthey occur hasnot been available. h p p ein nn d t0 he other end of The presentinvention provides apparatus for that gauge and to a second pressuregauge. In

detecting leaks in drill pipes before they reach such case, the twogauges may be connected to serious proportions. -The apparatus of my inasuitable indicator, in such fashion that their vention respondsimmediately to the presence of movements pp e ch o h r. The indicator isleaks in the drill stem and to the presence of set at zero or some othervalue while th amp obstructions in the system caused by cave-ins ingoperation i proceeding and while there are or the like, but issubstantially insensitive to no leaks in the drill pipe. Thereafter, ifa leak other changes which occur in the drilling' system occurs in thedrill pipe the indicator will deflect as normal incidents of operation.Thus, the in one direction. If an obstruction in the drillapparatusdistinguishes between variations in ing circuit occurs as a result ofcaving walls, or flow conditions due to the presence of a leak in otheraccident, the indicator will deflect in the the drill stem andvariations due to the presence 'opposite direction. I of obstructions,such as those occasioned by cave- The theory of operation of myinvention isins and is substantially unaffected by changes in 5demonstrated mathematically by the following rates of flow or pressureinthe drilling system equations, which relate to a well drilling systemthat are incident to increased depth of hole, in which a Venturi tube isprovided in the conpump regulation and wear and normal variations duitthrough which drilling fluid is forced to the in the density of thedrilling mud. More parbottom of the well andinwhich: ticularly,alteration of the speed of the mud 40 e r pumps brought about by openingor closing of the 1 i gg gg gg ii gfiig of Venturi throttle valve andchange of volumetric efliciency Pa=pressure at upstream end of theVenturi of the pumps due to wearing of parts do not KA=hydrau1icconstant of entire fluid circuit affect d c i apparatustween the pointat which P2 is taken and In accord ce wlth y inventlon, detectwn thepoint at which the drilling fluid releaks in a drill pipe duringdrilling operations turns to the atmosphere i accomplished by provid gan Obstruction (by Ks=hydraulic constant of Venturi tube means of aVenturi tube, Orifi e Plate Similar Ici=constant of gauge employed tomeasure P2 flowe device) in the drill Pipe equiv k2=constant ofdifferential gauge employed to alent conduit that supplies drillingltluidbto :2 measure p minus 91 bit, determining the pressures exer ed ye K0: 0 drilling fluid at the point of obstruction and at a g gjigfigjggi figgfigf wen arming, a neighboring but less obstructed point in the 2drill pipe and observing variations in the rela- 52] i tionship of thepressures so determined. Thus, K4 k2 I have found that the diiferentialbetween the D1=defle tion of ga e measuring pressure P2 pressure at thepoint of obstruction and the D2=deflection of gauge measuringdifferential pressure at a substantially unobstructed point pressure (P:minus Pi). ahead of the obstruction in the drill pipe bears Q=rate offlow of fluid in circuit including V Equations (2) Q=Ks(P. P

n z" B( 2 1) and K 2 (3) P2=[ fi' ar- 1) Pg-H D P2 P1=E substituting:(4) and (5) .in (3) Pm .22

so I

KB 2 k D.= 1- -1 or o z The value of Kodepends upon the values of I01,10:, KA and KB. The two former are instrument constants and areunaffected by changes in the'drilling circuit; KA and KB are affected bychanges in the density of the fluid in the ,circuit, but these changesare small in practice .and substantially equal so that there is butlittle in the drill pipe, or (b) an obstruction occurs in the hole. Incase (a) the ratio D1/D2 will change in one direction; in case (b) theratio will change in the opposite direction. I

These and other features of my invention will be more thoroughlyunderstood in the light of the following detailed description, taken'incon- Junction with the accompanying drawings in which: l

I Fig. 1 is a diagram of a well drilling system in which the drill pipeis equipped with one form of the leak-detection apparatus of myinventioni Fig. 2 illustrates one type of indicator for use in comparingthe values D1, Dz determined by the respective gauges;

- Fig. 3 illustrates another type of indicator for 6 comparing thevalues D1 and D2; and

Fig. 4 illustrates a spring mechanism which may be employed to vary thedeflection constants K1, is: of the respective gauges, so that the valueof K0 in any instance may be set at unity or at any other desired value.

Referring to the drawings the reference numeral ldesignates a cased wellin which is arranged a drill stem 2 consisting of a number of sectionsor "drill pipe. A bitor cutting tool I is arranged on the lower end ofthe drill pipe in the usual manner. In drilling, the drill pipe isrotated by a suitable rotary rig (not shown). A drilling fluid pipe 4 isconnected to a pump or pumps (not shown) by means of which drillingfluid or mud is fed through the drill pipe to the bit in the usualmanner. The drilling fluid, when it reaches the bottom of the drill pipepasses upstruction B in the drilling fluid pipe. In the in-' stant casethe obstruction is provided by a Venturi tube, although an orifice plateor any other equivalent element may be employed for this purpose. A pipeor tube is connected to the drilli-ng fluid pipe at the point ofobstruction (the throat of the Venturi) and to one end of a pressuregauge 8. At a point in the drilling pipe preceding the obstruction asecond pipe or tube 9 is connected to the drilling fluid pipe and theother end of this tube is connected to one end of a pressure gauge III.The tube 9 is also provided with a branch H which is connected to thegauge 8.

at the end opposite the tube 1.

Although any form of pressure gauge may be employed, I have illustratedgauges formed of cylinders with a piston l2 arranged in the gauge 8 anda similar piston l3 arranged in the cylinder l0. Pistons l2, l3 arebonnected to an indicator hand l4 by links l5 l6, respectivey, and theselinks are surrounded by springs l1, I8 which tend to hold the indicatorhand in the position corresponding to zero on a scale (not shown) to beused with the indicator hand.

The springs l1, l8 preferably are so constructed that their deflectionper unit load can be varied,

in order that the value K0 may be set at unity or any desired valuewithout the necessity of changing springs. A. referred type of springstructure for this purpose is described in detail hereinafter and isshown in Fi 4.

It will be apparent that the apparatus of Fig. 1 provides mechanicalmeans for automatically comparing the relationship of the deflectionsD1, D2 of the gauges 8 and I0, respectively. The gauges oppose eachother so that the pointer It remains stationary as long as D1 and D2 areequal. If, however, a leak occurs in the drill stem, or if anobstruction occurs in the path of the drilling fluid the change indrilling condition will be indicated by movement of the hand I.

The apparatus, in eifect, combines the action of-a Venturi tube or otherobstruction in the drilling fluid pipe for increasing velocity head andthe action of a static pressuregauge to the end that a positiveindication of leaks or caveins is immediately obtained, but irrelevantchanges in operating conditions do not affect the V apparatus. Thus, theinstrument is not affected '"'=by speeding up or slowing down of thepumps due to wearing of the parts. Change of mud 5 weight within theusual limits will not cause a change to be shown on the indicator l4. 1Because the apparatus indicates a change in the hydraulic constant? ofthe drill stem, it should be .set at atime when ,it is known that thereare no leaks in the drill stem. Thus, the instrument may be calibratedwhen the drill stem is first run into the hole, at which time it is safeto assume that there are no leaks. As additional sections of drill pipeare added to the drill stem,

the indicator will shift in a clockwise direction I to a higher value.This will be expected. But, any shifting to a lower value afteroperating with a given amount of drill pipe indicates a leak and warnsthe operator that the drill stem should be removed before a seriouswashout occurs, with resultant breakage of the stem and consequentfishing operation.

. Although in Fig. 1 the pressure gauges illustrated are piston andcylinder gauges, any conventional type of gauge may be employed. It ismerely necessary that the pressures P1 in the tube 1 and P2 in the tube9 operate to produce opposite effects in the pressure gauge 8 and thatthe resulting diflerential pressure (Pa-P1) be compared or contrastedwith the pressure P2 indicated by the gauge Ill.

In the apparatus of Fig. 1, the differential pressure (P2-P1) and thepressure P2 are compared or contrasted by means of the indicator [4which is actuated by the two opposing gauges. Such a mechanical meansfor comparing deflections is convenient but not essentialas will beapparent from consideration of the apparatus-of Fig. 2.

The apparatus illustrated by Fig. 2 is the same in principle as that ofFig. 1, but employs different mechanical means for comparing the gaugedeflections. Thus, the obstructed portion of the venturi 6 (P1) isconnected by the tube to a bellows mounted in a balancing frame 2| tooppose a bellows 22 that is connected to the unob-, structed drill fluidpipe 4 (P2) by the tube branch I I. Another branch of the pipe 9 alsosupplies P2 to a third bellows 23.

The balancing frame responds to variations in the differential pressure(Pa-P1) and its net movement is communicated by an arm 24 (the movementof which is restricted by a spring 25) that is connected to a bellowsgauge 26 filled with liquid which rises and falls in a tube 21 as thedifierential pressure (Pz-P1) changes.

have fixed deflection constants which are different for the two gauges.If so, the movable ruled sheet must be provided. If springs havingcontrollable deflection constants are employed,

these constants may be varied until the heights of the two liquidconstants are equal. The springs are setat the values thus arrived at,and thereafter the heights of the columns may vary but will remainsubstantially equal for a given length of drill stem unless a leakoccurs therein or a diminution of flow is caused by a cave-in or thelike. In the former case (leak), D1 will fall below D2; in the lattercase (cave-in) D2 will fall below D1.

The apparatus of Fig. 3 is a modification of the apparatus of Fig. 2,like parts being indicated by the same reference characters, but is ofthe recording type. To this end, it includes a rotatable indicator dialand a pair of pens 42, 4| that are in contact with the dial and aremounted upon levers that are actuated, respectively, WP: and (Pa-P1) sothat the deflections Di. and D2 are recorded on the dial as shown. Thepen 42 is mounted on the lever 43 which has a pivot 44.

The other end of the lever 43 is connected to the arm 28 of the bellows23 which varies as Pa. The pen 4| is mounted on the lever 45 which has apivot 46. The opposite end of the lever 45 is attached by means of anarm 41 to a. float 48 that rides at the surface .of a column of liquid49 in a tankill. The level of the column of liquid in the tank rises andfails because the tank is connected to the liquid column 21 of the b'el-A lows gauge 26.

Otherwise, the apparatuses of Figs. 2 and 3 are substantially the same.Thus, the junction point of the bellows 20, 22, the bottom of the spring25, the bottom of the spring 29, the top The bellows 23 responds tovariations in the the tops of the springs 25, 29 and the tops of thebellows 26, 30, are fixed to a base 32, that is partially shown.

The two gauge tubes are disposed substantially parallel to each other ona chart 33 provided with a series of ruled lines radiating from a pointon the lower'margin of the chart. The chartmay be moved lengthwise asindicated by the arrow, and may be constructed as an endless beltmounted on rollers (not shown).

The operation of the apparatus of Fig. 2, briefly, is as follows:

At a period during drilling operations when it is known that there areno leaks and while fluid is passing in the pipe, the ruled sheet isshifted lengthwise until the tops of both liquid columns be on the sameline. Thereafter, it the top of the liquid column -(Dl) reflecting P2falls on a line above-that reached by the top of the other liquid column(D2) reflecting (Pa-P1). there is an obstacle in the drilling circuitsuch as would be caused by a cave-in. If D1 falls on a line below thatreached by D2, there is a reduction in, the hydraulic constant Ksbrought about by a leak in the drill stem. Each time an additional drillpipe is added to the string, the apparatus should, of course, bere-calibrated.

In the apparatusof Fig. 2, the springs may of the bellows 23 and the topof the bellows'26 are all flxedby being; attached to the frame or base32, upon which the tank so and the pivots 44, 46 also rest.

The springs 25, 28 in the apparatus of Fig. 3, like those of Fig. 2, arepreferably adjustable, i. e., their constants of deflection per unit ofweight should be variable. If the apparatus of -Fig. 3 is provided withadjustable springs, the

deflections D1 and D2 shouldbe made equalfor a normal condition ofdrilling in which there are no leaks or abnormal restrictions in thedrilling circuit. substantially equal for a considerable time asdrilling progresses and for a given length of drill pipe there will Beno abrupt change in the relationship of D1 and D2 unless a leak orcave-in occurs. If D]. suddenly increases with respect to D2, in cave-inor the like is indicated. If D: be-

. comes greater than D1, a leak is indicated.

The springs 25, 29 in the apparatus of Figs. 2 and 3 are showndiagrammatically. A preferred form of spring structure which permits thedeflectidn constant to be varied is shown in Fig. 4.

This type of spring structure should be employed in the positions shownby the springs in positions 25, 29.

' Referring to Fig. 4, it will be observed that a conduit, for example,a branch of the tube -9 is connected to a bellows, for example, thebellows 23 mounted on the base 32. A rod, for example, the rod 28 isfastened to the other end of the bellows. The rod 28 is attached at itscenter to a leaf spring 50 which extends substantially horizontally incontact with knife edges N, 82, and controls the'movement of the rod.These knife edges are. fastened to threaded sliders 63, 84 andThereafter, D1 and D2 should remain may be moved back and forth from thecenter 01 the spring by means of the adjusting screw 65,

the two ends of which are threaded oppositely into the respectivesliders. The adjusting screw is journalled at its ends in thrustbearings in a base member 66 which is slotted'to provide tracks for thesliders.

Thedeflection constant of the leaf spring 60 can be changed at will byturning the adjusting screw so that the efiective length of the springbetween knife edges 6|, 62 is changed. If the apparatus of Fig. 2 or theapparatus of Fig. 3 is equipped with the spring structure shown in Fig.4, the deflections D1 and D2 may be 'made equal for any set ofconditions, i. e., the constant" Ko may be set at unity or any otherdesired value.

It will be apparent that manyother types of indicating mechanisms, bothmechanical and electrical; may be employed in place of those shown,without departing from the concept of my invention. Thus, electricalindicators, such as electrical strain gauges, may be employed.

connection communicates whereby static pressure ing drilling fluid tothe drill pipe at a substantially constant rate, an obstruction in thedrilling fluid delivery means, a pressure gauge having one sideconnected to the delivery means at the point of obstruction and theother'side connected. to

the delivery means at a point neighboring the obstruction, a secondpressure gauge connected to the delivery means at the second point, andindia pressure gauge, a connection between the Venturi tube and one sideof the pressure gauge, a

. second connection between the drilling fluid pipe at a point precedingthe Venturi tube and the opposite side of the pressure gauge wherebydifferential between static pressure and the pressure at the throat ofthe Venturi tube is obtained; a second pressure gauge with which saidsecond of the drill pipe is obtained, and indicating means controlled bythe combined action of the two gauges.

ROBERT LGARDNER.

